* Check for damage on and to the side walls.
This last point was demonstrated brilliantly to viewers on Ireland AM recently by Fergal Eiffee of the ITIA.
He showed presenter Alan Hughes an example of a tyre that, upon first glance and appearance, looked fine.
The tread depth was good, not even close to the minimum depth level of 1.6mm.
But, on closer inspection, Fergal pointed out that there was a bulge on the side wall of the tyre, probably caused when the vehicle drove through a pothole or clipped a footpath.
Whatever the cause, the tyre was in danger of having a blowout.
Can you imagine that happening if you were driving on the motorway? Well, you didn't have to. Fergal had an example to show. The tyre was in shreds.
And that leads neatly to the whole issue of second-hand or part-worn tyres.
They may look fine - i.e. have 6mm of tread depth (a new one has 8mm) - but they could have damage that's hidden to the untrained eye.
We wanted to find out more about the quality and value of used tyres being sold on the market here.
So we teamed up with the AA to conduct a 'mystery shopping' exercise. It targeted 60 tyre retailers across the country during the summer.
Of the 60 retailers visited, 30 offered second-hand tyres for sale.
The findings are worrying.
Half the second-hand tyres that were purchased showed signs of damage in the road contact surface area.
While not immediately unroadworthy, such damage (for example, puncture repairs and scuffs) can lead to weaknesses and increase the likelihood of failure down the line.
Just more than two out of five tyres bought were six years or older - an advisory warning at the NCT.
Around 44pc were found to be stored in unsuitable environments - incorrectly stacked on top of each other and/or exposed to the elements.
Almost two-out-of-three retailers also failed to inform the buyer whether or not the tyres were inspected and roadworthy.
While the findings are a concern, it's important to highlight that many retailers were themselves wary of selling the second-hand tyres. Some even attempted to dissuade our buyer, offering them new tyres instead.
So, from that perspective, it's encouraging to see more and more Irish tyre retailers making safety a priority by choosing to sell only new tyres.
None of the retailers who sold us a used tyre were members of either the ITIA or the Society of the Irish Motor Industry.
You simply don't know the history of a used tyre or how it will perform, so why risk it?
Most people buy used tyres because they think they're saving money when, in reality, they're probably not.
During the mystery shopping event, the average price of a second-hand tyre was €34.
Yet an extra €26 would buy a new budget tyre that wouldn't need to be replaced as soon.
So, in the long run you are paying more for a used tyre because you have to replace it sooner.
My advice is to give used tyres a miss.